The invention relates generally to the field of energy harvesting, and more particularly, to energy harvesting circuits for reducing battery drain.
Energy harvesting is a process for recovering power that is otherwise dissipated or lost in a system. For example, energy harvesting may be used to obtain energy from solar activity, wind, thermal sources, wave action, water currents, and the like. Similarly, energy may be harvested from other sources, such as motor vibrations, pressure changes in the soles of shoes, and the like. In many systems, harvested energy may be used in conjunction with battery power to provide power to a load, such as a sensor or the like. Harvested energy may be used to power the load under normal conditions, with power from the battery being used as a supplement during periods when harvested energy is insufficient to fully power the load. Such systems may extend the useful lifetime of the battery.
Some systems utilize excess harvested energy to recharge the battery in an attempt to further maximize battery life. However, this requires a rechargeable battery for functioning. One drawback with rechargeable batteries is that they have low useful battery life compared to non-rechargeable batteries if there is insufficient harvested energy to recharge the battery.
Other systems utilize a harvesting energy source along with non-rechargeable batteries. In such systems, non-rechargeable batteries are primarily used to prolong the continuous delivery of power to the system. These systems may accidentally charge the battery or deliver an accidental charging current to the battery. Because, the life of non-rechargeable batteries may be affected if they are charged or if they receive a charging current, such systems are not effective for long-life applications. An improved circuit for utilizing harvested energy to power a load in conjunction with a battery is desirable.